The invention relates to a heating heat exchanger in the engine cooling circuit of a motor vehicle, with a forward-flow pipe opening at the top into a water box and with a vent line of small cross-section which is assigned to the forward-flow pipe and which is guided to a compensating tank and there terminates below the liquid level.
An arrangement of this type, with a horizontally disposed heat exchanger through which the flow therefore passes horizontally and which is intended for the separation and elimination of gaseous constituents carried along in the engine cooling circuit, is known form British Patent Specification 918,221. From the compensating tank adjacent to the forward-flow water box, the vent line leads into the mouth region of the forward-flow pipe, so that in each case a part stream of cooling liquid mixed with gas bubbles enters the vent line and is conveyed to the compensating tank where the gaseous constituents can bubble out. The layout of the vent line within the heat exchanger involves a high expense. Also the efficiency of such an arrangement is not especially high, since gas separation occurs only at higher flow speeds, whereas, at low flow speeds, the gas bubbles are transported along the upper pipe wall of the forward-flow pipe and consequently cannot enter the vent line leading away at a lower level. Thus, when the heat exchanger is used as a heating heat exchanger with a low heating capacity cooling liquid mixed with the gas being still always transported, this arrangement causes an annoying gurgling and sloshing noise in the vehicle interior. The conditions are even more unfavorable when the heat exchanger is arranged upright and the flow passes through it from the top downwards.
An object of the invention is to provide a venting facility which has a simple construction and can be connected easily and which separates the greatest possible amount of gas, particularly also at low flow speeds, so that gurgling and sloshing noises are avoided.
In a heat exchanger of the above-noted type, this object is achieved by providing an arrangement wherein the vent line is brought into the operative position together with the fastening of the forward-flow pipe and leads away from the highest point of the forward-flow water box to a compensating tank spaced therefrom. Components built into and onto the heat exchanger are therefore restricted to a minimum. Because the forward-flow pipe and the vent pipe are connected simultaneously, there is no need for any special connection measures as regards the vent line. Because the connection of the vent line is placed high there is an especially good discharge of cooling liquid mixed with gas.
In a preferred exemplary embodiment of the invention necessitating no modifying measures at all on the forward-flow water box, the vent line enters the forward-flow pipe from above, with angling, on the heat-exchanger side and comes out of the latter on the mouth side thereof.
In another exemplary embodiment of the invention, a collecting space from which the vent line leads away is formed above the opening of the forward-flow pipe into the forward-flow water box.
When the heat exchanger is equipped with at least one return-flow water box incorporated in the upper forward-flow water box and partitioned off by walls, the degree of gas separation can be increased by including at least one high-placed overspill orifice of small width in the separating wall partitioning off each return-flow water box from the forward-flow water box.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.